Encapsulated transducer having a protective sleeve

ABSTRACT

An encapsulated transducer (10) includes an injection molded encapsulation (20) having a front end (22) and a back end (24). The encapsulation (20) is a monolith of cured moldable material ensconcing a sensing element (90) proximate the front end (22) and a portion of an information transmitting medium (120) emanating from the back end (24). A component alignment preform (40) operatively couples the sensing element (90) with the information transmitting medium or cable (120). The component alignment preform (40) includes a front ferrule (70) and a rear ferrule (80) bonded thereto and linearly spaced apart along a long axis &#34;A&#34;. The component alignment preform (40) further includes an annular recess (44) in which the sensing element or coil (90) is placed so that it is linearly spaced and aligned along the common long axis &#34;A&#34; in which the front and rear ferrules (70), (80) are aligned. A first lead (98) of the coil is electrically connected to the front ferrule (70) and a second lead (100) of the coil (90) is electrically connected to the rear ferrule (80). A back end (48) of the component alignment preform (40) receives a stripped end (122) of the cable (120) such that a center conductor (126) mates with the front ferrule (70) and a coaxial conductor (130) mates with the rear ferrule (80). The respective conductors (126), (130) are electrically and mechanically connected to the pair of front and rear ferrules (70), (80). A protective sleeve (150) is then fitted over the coil (90) thereby forming a sleeved coil and cable assembly (170). This sleeved coil and cable assembly (170) is encapsulated by an injection molding process which provides the durable encapsulation (20) which bonds with itself and with the sleeved coil and cable assembly (170). The sleeved coil and cable assembly (170) is symmetrically disposed within the encapsulation (20) and the encapsulation (20) includes an integrally formed protective wall having an uniform thickness &#34;T&#34; along a forwardmost portion of the sensing element (90).

This application is a division of application Ser. No. 08/542,522, filedOct. 13, 1995, now U.S. Pat. No. 5,685,584.

FIELD OF THE INVENTION

The present invention relates generally to an encapsulated transducerwith a component alignment preform and, in particular, to anencapsulated transducer substantially impervious to adverse mechanical,physical or chemical aggressions from the surrounding environment andmethod of manufacturing such transducer which is used to monitorvibration of rotating machinery, temperature sensing and the monitoringand sensing of other physical phenomenon.

BACKGROUND OF THE INVENTION

Monitoring and diagnosing the status of rotating and reciprocatingmachinery start with accurate and dependable measurements from atransducer and its associated electronics and then proceed to othersophisticated analyzing apparatus for reduction and display. One suchtransducer is a proximity transducer which may be utilized for, interalia, monitoring the vibration characteristics of a rotating shaft of amachine. In this environment, the transducer must operate under veryadverse physical, chemical and mechanical conditions and it is oftenvery difficult to replace such transducers. Thus, there is an ongoingeffort to make the proximity transducer one of the most reliable partsof the monitoring system.

Typically, the proximity transducer, in conjunction with associatedelectronics, outputs a signal correlative to the spacing between anobject or "target" (the rotating shaft of the machine) and a sensingcoil of the proximity transducer. It is critical that the length orspacing between the target and the sensing coil of the proximitytransducer remains within the linear range of the transducer forproviding accurate and reliable measurements when in operation. Thus,the hallmark for providing accurate and reliable measurements relies onproviding a transducer which is impervious to the predations of theenvironment and which does not consume an inordinate amount of thelinear range of the transducer.

The following prior art reflects the state of the art of which applicantis aware and is included herewith to discharge applicant's acknowledgedduty to disclose relevant prior art. It is stipulated, however, thatnone of these references teach singly nor render obvious when consideredin any conceivable combination the nexus of the instant invention asdisclosed in greater detail hereinafter and as particularly claimed.

    ______________________________________                                        U.S. PATENT DOCUMENTS                                                         DOCUMENT NO.  DATE          NAME                                              ______________________________________                                        2,361,348     October 24, 1944                                                                            Dickson et al.                                    2,890,505     June 16, 1959 Brand                                             3,932,828     January 13, 1976                                                                            Plunkett et al.                                   4,000,877     January 4, 1977                                                                             Shead et al.                                      4,162,138     July 24, 1979 Byrne                                             4,377,548     March 22, 1983                                                                              Pierpont                                          4,408,159     October 4, 1983                                                                             Prox                                              4,419,646     December 6, 1983                                                                            Hermle                                            4,470,786     September 11, 1984                                                                          Sano et al.                                       4,680,543     July 14, 1987 Kohen                                             4,829,245     May 9, 1989   Echasseriau et al.                                4,954,307     September 4, 1990                                                                           Yokoyama                                          4,959,000     September 25, 1990                                                                          Giza                                              5,016,343     May 21, 1991  Schutts                                           5,018,049     May 21, 1991  Mehnert                                           5,021,737     June 4, 1991  Schutts                                           5,039,942     August 13, 1991                                                                             Buchschmid, et al.                                5,049,055     September 17, 1991                                                                          Yokoyama                                          5,122,046     June 16, 1992 Lavallee et al.                                   5,133,921     July 28, 1992 Yokoyama                                          5,138,292     August 11, 1992                                                                             Forster                                           5,147,657     September 15, 1992                                                                          Giza                                              5,151,277     September 29, 1992                                                                          Bernardon, et al.                                 5,182,032     January 26, 1993                                                                            Dickie et al.                                     5,226,221     July 13, 1993 Kilgore                                           5,240,397     August 31, 1993                                                                             Fay et al.                                        5,252,051     October 12, 1993                                                                            Miyamoto et al.                                   5,351,388     October 4, 1994                                                                             Van Den Berg, et al.                              5,376,325     December 27, 1994                                                                           Ormson                                            ______________________________________                                        FOREIGN PATENT DOCUMENTS                                                      DOCUMENT NO.  DATE          COUNTRY                                           ______________________________________                                        UK 1 313 748  April 18, 1973                                                                              Great Britain                                     UK 1 353 603  May 22, 1974  Great Britain                                     JA-139710     August 6, 1978                                                                              Japan                                             WO 84/03794   September 27, 1984                                                                          PCT                                               FR 2576-245-A July 25, 1986 France                                            JA 6-37130-A  October 2, 1994                                                                             Japan                                             ______________________________________                                    

The two patents to Schutts and the patent to Van Den Berg, et al.reflect assignee's ongoing commitment to providing an accurate sensorwhich is impervious to predations of the environment.

The French patent to Jaeger teaches the use of a method and apparatusfor injection molding of an elongated detector with a sensor at one end.One end of the detector is supported by the mold while the sensor end isengaged by a centering sleeve (130). The centering sleeve (130)terminates in a piston (132) which is mobile in a cylinder (126) andslides about a fixed rod (138). Thermoplastic is injected into the moldand the centering sleeve is removed from the sensor when the injectionprocess is only partially complete.

The Japanese patent to Kawakami teaches the use of sealing asemiconductor chip by transfer molding. A semiconductor chip (4) ismounted on a carrier (1) and is held at a fixed position via mobile pins(17) and (18). The mobile pins (17) and (18) are movably fitted to a topforce (11) and a bottom force (12) for freely advancing or retractingthe pins into and out of the cavities (15) and (16). While the pins (17)and (18) are in contact with the carrier (1), a resin (20) is injectedinto the cavities (15) and (16) through gates (13) and (14) and the pins(17) and (18) are gradually retracted in accordance with the injectingstate of resin (20).

The patent to Yokoyama teaches the use of an apparatus for manufacturingplastic encapsulated electronic semiconductor devices. A support pad(11) is firmly fixed by first and second sliders (24A) and (24B) andalso by mold halves (19) and (20). The first and second sliders (24A)and (24B) are moved outwardly of a cavity (25) when the cavity is halffilled with the plastic encapsulating material. Spaces, which are formedafter movement of the sliders, are filled with the plastic encapsulatingmaterial directly poured through a gate (23). It should be noted thatthe sliders (24A), (24B) perform two functions in the cavity (25). Thefirst function is to firmly grasp a thin end portion of the support pad(11) thereby fixing same in position and the second function is tonarrow a passage through the gate (23).

The patent to Pierpont teaches the use of a method for encapsulating anelectrical component having radial leads. A large multi-cavity mold isloaded with a plurality of horizontal radially leaded capacitors. Theclosed mold grips the leads (15). A top pin (25) pushes each componentbody downward a predetermined degree so that each body is left in aboutthe same position within the corresponding mold cavity. A bottom pin(28) then pushes each component body upwardly only slightly above acenter of the mold cavity so that upon bottom pin withdrawal, stresseswithin the lead wires of the electrical component cause the componentbodies to spring back just to the mold cavity center portion. Moldingresin is then introduced.

The other prior art listed above, but not specifically discussed, teachother sensor devices and molding processes and further catalog, theprior art of which the applicant is aware. These references diverge evenmore starkly from the references specifically distinguished above.

SUMMARY OF THE INVENTION

The present invention is distinguished over the known prior art in amultiplicity of ways. For one thing, the present invention provides atransducer including a protective seamless encapsulation ensconcing asensing element at one end and a cable extending out of the other end.In addition, the sensing element is symmetrically disposed about a longaxis of the transducer and the seamless encapsulation includes anintegrally formed protective wall having an uniform thickness along aforwardmost portion of the sensing element.

Preferably, the sensing element is in the form of a sensing coil havinga front face, a back face, a body having an outer surface and a centervoid extending through the body and at least a first lead and a secondlead extending from the sensing coil and spaced from one another. Thebody of the coil extends between the front face and the rear face. Thecable is preferably a triaxial cable comprised of an outer protectivejacket circumscribing an interior of the cable which includes threeconcentrically disposed conductors separated from one another by atleast two concentrically disposed insulators. Specifically, the outerprotective jacket circumscribes the concentrically disposed triaxial,coaxial and center conductors which are in turn separated from oneanother by an insulator and a dielectric interposed between the triaxialand coaxial conductors and the coaxial and center conductors,respectively. At least one end of the cable is stripped in a step-likefashion to expose a length of the center conductor, the dielectric, thecoaxial conductor, the insulator and the triaxial conductor.

In addition, the encapsulated transducer includes a front ferrule havinga bore with an inner diameter substantially equal to the outer diameterof the center conductor and a rear ferrule having a bore with an innerdiameter substantially equal of the outer diameter of the coaxialconductor.

A component alignment preform is molded in a single step. The componentalignment preform includes an annular recess having a center postaxially aligned with the front and rear ferrules which are bonded to thepreform and linearly spaced apart along a long axis of the preform.

Once the preform has been molded, the sensing coil is placed over thecenter post and in the annular recess. The sensing coil is thenelectrically connected to the ferrules. This is accomplished byresistance welding the first lead of the sensing coil to the frontferrule and the second lead of the sensing coil to the rear ferrule.

Then, the stripped end of the cable is inserted into the bores of themolded together front and rear ferrules. The center conductor ismechanically and electrically connected to the front ferrule and thecoaxial conductor is mechanically and electrically connected to the rearferrule thereby forming a sensing coil and cable assembly. A protectivesleeve is fixed over the sensing coil, thus forming a sleeved coil andcable assembly.

Once the process of forming the sleeved coil and cable assembly iscompleted, the sleeved coil and cable assembly is ready to beencapsulated using an injection molding process. The injection mold isdefined by an upper mold plate having an upper cavity and a lower moldplate having a lower cavity. The upper and lower cavities form a moldcavity when in the closed position which is complementary to the desiredform of the encapsulation of the sleeved coil and cable assembly. Themold cavity is defined by an upper wall, a lower wall, a front wall anda back wall having an opening extending therethrough. Preferably, theupper mold plate and the lower mold plate are each provided with atleast one slideable support pin which extends into the respective upperor lower cavity of the mold and when retracted conform with therespective upper or lower wall of the mold cavity to provide the desiredform of the encapsulation. In addition, a slideable locator pin isprovided adjacent the front wall of the mold cavity and is capable ofextending into and out of the lower cavity when the mold is in an openedposition.

The sleeved coil and cable assembly is placed into the lower cavity ofthe lower mold plate such that the cable of the sleeved coil and cableassembly extends out the opening of the back wall of the mold cavity. Atleast one slideable support pin is extended into the lower cavity of thelower mold plate and is placed in engagement with a portion of thesleeved coil and cable assembly therein. This supports and centers thesleeved coil and cable assembly within the mold cavity. In addition, theslideable locator pin is extended into the mold cavity such that itproperly locates the sensing coil within the mold cavity and spaces it apredetermined distance from the front wall of the mold cavity. Once theslideable locator pin has centered the coil and spaced it apredetermined distance from the front wall of the mold cavity, it iswithdrawn and the injection mold is closed. The slideable support pin inthe upper mold plate is extended into the upper cavity and comes intoengagement with a portion of the sleeved coil and cable assembly whenthe injection mold is closed. This provides additional means forsupporting and centering the assembly within the mold cavity such thatthere is a void completely surrounding the assembly (except of coursewhere the pins are touching the assembly). Note that the location andthe number of slideable support pins may be configured to best supportthe assembly being encapsulated within the cavity.

Once the mold is in the closed position a self-bonding moldable materialis injected into the mold cavity via runners and gates. This process iscontinued until the mold cavity is completely filled and the coil andcable assembly is completely ensconced within the moldable material. Theslideable support pins are then retracted within the respective upperand lower walls of the mold cavity prior to the moldable materialsolidifying. Note that an additional charge of moldable material may beinjected into the mold as the support pins are being withdrawn so as toaccommodate for any additional material needed to completely fill thevoids left by the previously extended support pins. Once the process ofinjecting the moldable material into the cavity is completed and thesupport pins have been retracted, the mold may be opened and theencapsulated transducer allowed to cool in the lower mold plate. Oncethe encapsulated transducer is cooled one or more bottom support pinsmay be actuated to eject the encapsulated transducer therefrom.Preferably the moldable material is polyphenylene sulfide (PPS) whichhas the characteristic of bonding to itself.

OBJECTS OF THE INVENTION

It is a general object of the present invention to provide an improvedtransducer and a method of manufacturing such transducer.

A primary object of the present invention is to provide an improvedencapsulated transducers with a component alignment preform and methodof manufacturing same.

A further object of the present invention is to provide an encapsulatedtransducer as characterized above which has an injection molded seamlessencapsulation ensconcing a sensing coil at one end and a cable extendingout of the other end, one end of the cable being electrically connectedto the sensing coil within the encapsulation and the other end connectedto an electrical processing unit distal from said encapsulation.

Another further object of the present invention is to provide anencapsulated transducer as characterized above wherein the encapsulationprovides a seamless sealing envelope around the sensing coil and an endportion of the cable, thus providing an impervious seal against anymechanical, physical or chemical aggressions from the surroundingmedium.

Another further object of the present invention is to provide anencapsulated transducer as characterized above which is comparativelyless expensive to manufacture than existing transducers for use inmonitoring and diagnosing the status of rotating and reciprocatingmachinery and which also lends itself to rapid mass productiontechniques.

Another further object of the present invention is to provide a preformwhich substantially axially aligns the sensing coil with the front andrear ferrules and the respective conductors of the cable.

Another further object of the present invention is to provide anencapsulated transducer as characterized above wherein the sleeved coiland cable assembly is centered within the encapsulation and wherein adistance between the front face of the sensing coil and a front face ofthe encapsulation is held to a very close tolerance which isreproducible from one transducer to another in mass production.

Another further object of the present invention is to provide anencapsulated transducer as characterized above wherein the encapsulationstrongly bonds to the sleeved coil and cable assembly for providing aleak tight seal and resisting axial forces applied to the encapsulationor cable which may cause the electrical connections to completely orpartially break resulting in an inoperative or unreliable transducer.

Another further object of the present invention is to provide anencapsulated transducer as characterized above which is capable of beingmass produced with reproducible operational characteristics withoutappreciable alterations of the signals they admit when in operation.

Another further object of the present invention is to maintain apredetermined linear range capability for each manufactured transducer.

Another further object of the present invention is to provide aslideable locator pin which centers the coil within the mold cavity andspaces the front face of the coil from the front wall of the mold cavityprior to the injection molding process.

Another further object of the present invention is to provide aplurality of slideable support pins for supporting and centering thesleeved coil and cable assembly during the injection molding process.

Viewed from a first vantage point it is an object of the presentinvention to provide an information transmitting sensor and housingcomprising: a sensing element; a cable coupled to the sensing element; acomponent alignment preform operatively coupled to the sensing elementand the cable; a protective sleeve extending from the sensing elementover the preform and towards the cable; and a monolith of cured moldablematerial ensconcing the sensing element and a portion of the cabledefining a seamless mass circumscribing the sensing element and aportion of the cable.

Viewed from a second vantage point it is an object of the presentinvention to provide an encapsulated transducer for use in monitoringthe status of rotating equipment in a harsh environment with a componentalignment preform having a leading end with an active element and atrailing end with an information transmitting medium emanatingtherefrom, formed by: fixing an abbreviated protective sleeve over theactive element and a portion of the component alignment preform;integrally forming a locating means proximate the leading end of thepreform; locating the active element in a mold cavity with the locatingmeans coupled thereto, assuring proper registry in the mold cavity;integrally forming a supporting means proximate the component alignmentpreform; further supporting the active element and the componentalignment preform in the mold cavity with the support means and removingthe locator means; molding over the active element, the protectivesleeve and the preform of the sensor with a moldable material except foran area of support; removing the support means; injecting moldablematerial adjacent the support means for filling in the areas heretoforeoccupied by the support means; whereby the active element is preciselylocated in a moldable material to accurately address the rotatingequipment.

Viewed from a third vantage point, it is an object of the presentinvention to provide a transducer for monitoring the status of rotatingequipment wherein a shaft of the rotating equipment is exposed to thetransducer, comprising, in combination: means for mounting thetransducer a distance from the shaft such that a tangent of the shaft isperpendicular to a long axis of the transducer, the transducer having asensing coil located proximate the shaft, a front portion of thetransducer including a protective wall having uniform thickness along aforwardmost portion of the sensing coil, the sensing coil symmetricallydisposed about the long axis, and a protective seamless encapsulationintegrally formed with the protective front wall ensconcing the sensingcoil and overlapping both a protective sleeve and a leading portion of acable operatively coupled to the sensing coil, the cable extending awayfrom the transducer to an electrical processing unit.

Viewed from a fourth vantage point, it is an object of the presentinvention to provide a process for making a transducer, comprising thesteps of: providing a sensing coil having a center void, a front face, arear face and at least a first lead and a second lead extending from thesensing coil; providing a cable having at least one outer conductorsurrounding at least one insulator carrying at least one centerconductor; connecting the cable to the core; stripping an end of thecable in a step-like fashion to expose a portion of the centerconductor, the insulator and the outer conductor; forming a front andrear pair of ferrules with the front ferrule having a bore with adiameter substantially matching the diameter of the center conductor andthe rear ferrule having a bore with a diameter substantially matchingthe diameter of the outer conductor; molding together in linearly spacedproximity with a self-bonding moldable material the front and rearferrules and providing in such molding step an annular recess near thefront ferrule and linearly aligned therewith and a chamber interposedbetween and in open communication with the front and rear ferrules,thereby forming a component alignment preform; inserting the coil in theannular recess and electrically connecting the first lead to the frontferrule and the second lead to the rear ferrule; inserting the strippedcable end into the bores of the molded together front and rear ferrulesand mechanically and electrically connecting the outer conductor to therear ferrule and the center conductor to the front ferrule, therebyforming a sensing coil and cable assembly; forming an abbreviated sleevehaving a first end with a substantially constant cross-sectional areaand a second end with a substantially constant cross-sectional areagreater than the first end, a body having a substantially smooth outersurface and a hollow inner bore defining an inner surface, the bodyextending between the first end and the second end; fixing the sleeveover the sensing coil thereby forming a sleeved coil and cable assembly;supporting and centering the sleeved coil and cable assembly within amold cavity with at least one slideable support; orienting the cable toextend out from the mold cavity; locating the sensing coil within themold cavity and spacing the front face of the sensing coil a distancefrom a front wall of the mold cavity with at least one slideablelocator; retracting the slideable locator from the mold cavity;injecting the self-bonding moldable material into the cavity of the moldto precisely ensconce the sleeved coil and cable assembly and providinga precise face thickness covering the face of the coil; retracting theslideable supports from the sleeved coil and cable assembly so that theself-bonding moldable material will flow into the areas heretoforeoccupied by the slideable supports; allowing the moldable material toset; and removing the thus formed transducer from the mold cavity as anintegrated unit having a seamless mass of moldable material ensconcingthe sleeved coil and cable assembly.

These and other objects will be made manifest when considering thefollowing detailed specification when taken in conjunction with theappended drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of an encapsulated transducer with acomponent alignment preform according to the present invention which isjuxtaposed to a rotating shaft of a machine for monitoring the vibrationthereof.

FIG. 2 is a partial sectional view of the encapsulated transducer withthe component alignment preform according to the present invention.

FIG. 3 is a cross-sectional exploded parts view of the componentalignment preform.

FIG. 4 is a cross-sectional view of a sensing coil and the componentalignment preform formed by the combination of the elements of FIG. 3.

FIG. 5 is a cross-sectional view of the combination of the elements ofFIG. 4.

FIG. 6 is a diagrammatic view of an assembly step of the presentinvention and a cross-sectional view of the combination of the elementsof FIG. 4.

FIG. 7 is a diagrammatic view of an assembly step of the presentinvention and a partial sectional view of the combination of theelements of FIG. 6.

FIG. 8 is a partial sectional view of the combination of the elements ofFIG. 7.

FIG. 9 is a simplified cross-sectional view of a mold in an openposition and having all included slideable support and locator pins inan extended position.

FIG. 10 is a view of the mold of FIG. 9 with the slideable support pinscentering and supporting that which is shown in FIG. 8.

FIG. 11 is a simplified cross-sectional view of the mold in a closedposition with the slideable locator pin retracted from engagement of thesensing coil.

FIG. 12 is a simplified cross-sectional view of the mold in a closedposition with the slideable support pins retracted after an injectionmolding according to the present invention is completed.

FIG. 13 is an elevational view of an injection mold used to mass producea plurality of encapsulated transducers sequentially.

DESCRIPTION OF PREFERRED EMBODIMENTS

Considering the drawings, wherein like reference numerals denote likeparts throughout the various drawing figures, reference numeral 10 isdirected to the encapsulated transducer with a component alignmentpreform according to the present invention.

In essence, and referring to FIG. 2, the encapsulated transducer 10includes an injection molded encapsulation 20 having a front end 22 anda back end 24. The encapsulation 20 is a monolith of cured moldablematerial ensconcing a sensing element 90 proximate the front end 22 anda portion of an information transmitting medium 120 emanating from theback end 24. A component alignment preform 40 operatively couples thesensing element 90 with the information transmitting medium or cable120. The component alignment preform 40 includes a front ferrule 70 anda rear ferrule 80 bonded thereto and linearly spaced apart along a longaxis "A" of the transducer 10. The component alignment preform 40further includes an annular recess 44 (FIG. 3) in which the sensingelement or coil 90 is placed so that it is linearly spaced and alignedalong the common long axis "A" in which the front and rear ferrules 70,80 are aligned. A first lead 98 of the coil is electrically connected tothe front ferrule 70 and a second lead 100 of the coil 90 iselectrically connected to the rear ferrule 80. A back end 48 of thecomponent alignment preform 40 receives a stripped end 122 (FIG. 6) ofthe cable 120 such that a center conductor 126 mates with the frontferrule 70 and a coaxial conductor 130 mates with the rear ferrule 80.The respective conductors 126, 130 are electrically and mechanicallyconnected to the pair of front and rear ferrules 70, 80. A protective"abbreviated" sleeve 150 (i.e. extending only from the coil 90 to thefront ferrule 70) is then fitted over the coil 90 thereby forming asleeved coil and cable assembly 170 (FIG. 8). This sleeved coil andcable assembly 170 is encapsulated by an injection molding process whichprovides the durable encapsulation 20 which bonds with itself and withthe sleeved coil and cable assembly 170. The sleeved coil and cableassembly 170 is symmetrically disposed within the encapsulation 20 andthe encapsulation 20 includes an integrally formed protective wall 26having an uniform thickness "T" along a forwardmost portion of thesensing element 90.

A leading portion of the transducer skin is cylindrical 2 near the coil90 and has a front wall 26 sealing the coil. Thereafter, the skin stepsdown 3, then diverges outwardly 4 and transitions to a cylindricalsection 5. Another instep 6 leads to a cylindrical section 7, thence toa ridge 9 flanked by an up slope 15 and a down slope 11, followed by along cylinder 12, terminating in an intaper 13, a cylindrical section 14and the back end 24 which grasps the cable 120 tightly.

More specifically, and referring to FIGS. 3 and 4, the componentalignment preform 40 is formed in a first injection molding processwhere the moldable material is preferably polyphenylene sulfide (PPS).The PPS material is a dielectric and thus an electrical insulatingmaterial which has the characteristic of bonding to itself. The frontand rear ferrules 70, 80 are preferably placed on a pin support within amold and the PPS material is molded around the front and rear ferrules70, 80 thereby forming the component alignment preform 40 as shown inFIG. 4. The front and rear ferrules 70, 80 are inner-locked and linearlyspaced apart along the long axis "A" by the PPS material. A front end 42of the preform 40 includes an annular recess 44 having a center post 46axially aligned with the front and rear ferrules 70, 80 along the longaxis "A". The preform 40 further comprises a chamber 50 including abridging section 54 of constant cross-sectional area extending between afront and a rear truncated cone 52, 56 which isolate the front and rearferrules 70, 80. The front ferrule 70 includes a bore 76 with an innerdiameter substantially equal to the outer diameter of the centerconductor 126. The rear ferrule 80 includes a bore 86 with an innerdiameter substantially equal to the outer diameter of the coaxialconductor 130. The ferrules 70, 80 are preferably formed from brass.

Referring to FIGS. 4 and 5, the sensing element 90 is preferably asensing coil 90 comprised of a front face 94, a back face 96, a body 102having an outer surface 104 and a center void 92 extending through thebody 102 and first and second leads 98, 100 extending from the coil 90and spaced from one another. The body 102 of the coil 90 extends betweenthe front face 94 and the back face 96.

Once the component alignment preform 40 has been formed, the sensingcoil 90 may be electrically connected to the respective ferrules 70, 80of the preform 40. This is accomplished by placing the sensing coil 90within the annular recess 44 of the preform 40 such that the post 46extends a distance within the center void 92 of the coil 90. The firstlead 98 is then preferably induction welded to the front ferrule 70 andthe second lead 100 is preferably induction welded to the rear ferrule80, thus forming a coil and preform assembly 110. Next, the cable 120 iselectrically and mechanically connected within the preform 40.

Referring to FIGS. 6 through 8, the cable 120 is preferably a triaxialcable comprised of an outer jacket 136 circumscribing an interior of thecable which includes three concentrically disposed conductors 126, 130and 134 separated from one another by at least two concentricallydisposed dielectrics or insulators 128, 132. More specifically, theouter protective jacket 136 circumscribes the concentrically disposedtriaxial, coaxial and center conductors 134, 130 and 126 which areseparated from one another by an insulator 132 and a dielectric 128interposed between the triaxial and coaxial conductors 134, 130 and thecoaxial and center conductors 130, 126, respectively. At least one end122 of the cable 120 is stripped in a step-like fashion to expose alength of the center conductor 126, the dielectric 128, the coaxial orouter conductor 130, the insulator 132 and the triaxial conductor 134.

Referring to FIG. 6, solder paste 140 is inserted into the bore 76 ofthe front ferrule 70 preferably, via a syringe which is pneumaticallydriven so as to dispense an uniform predetermined amount of paste 140which is reproducible every time. A solder ring 142 is placed onto thestripped end 122 of the cable 120. The solder ring 142 encircles thecoaxial conductor 130 and abuts the insulator 132 which is interposedbetween the coaxial and triaxial conductors 130, 134. An elastomericsleeve 144 is placed over the dielectric 128 of the cable 120 andincludes an inner diameter which substantially matches the outerdiameter of the dielectric 128. The elastomeric sleeve 144 may be of aninsulating material such as fluorosilicone rubber. The elastomericsleeve 144 has an outer diameter which is slightly larger than thebridging section 54. The cable 120 is then inserted into the back end 48of the component alignment preform 40 such that the center conductor 126fits within the bore 76 of the front ferrule 70 and the coaxialconductor fits within the bore 86 of the rear ferrule 80. An axial forceexerted as shown by the arrows F₁ and F₂, deform the elastomeric sleeve144 against the conical transition between the bridging section 54 andthe rear truncated cone 56. This provides a tight seal between thistransition area and the dielectric 128 of the cable 120 as shown in FIG.7. A permanent mechanical and electrical connection is made between thecoaxial conductor 130 and the bore 86 of the rear ferrule 80 and alsobetween the center conductor 126 and the bore 76 of the front ferrule70. The use of inductive heating, with the above forces F₁, F₂ beingapplied, causes the solder paste 140 and solder ring 142 to melt andflow over the exposed conductors 126, 130 and upon cooling fixes theexposed conductors 126, 130 permanently throughout their length to thebores 76, 86 of the front ferrule 70 and the rear ferrule 80respectively. Of course, rather than solder, an adhesive or welding maybe used. Note that the preformed amount of solder paste 140 and thepreformed solder ring 142 provide effective repeatability of theelectromagnetic characteristics of the entire encapsulated transducer10, especially with respect to the inductance parameter of the sensingcoil 90 which as illustrated is relatively close to the center conductor126.

Referring to FIG. 7, a protective sleeve 150 is preferably formed fromthe PPS material. The protective sleeve includes a first end 152 with asubstantially constant cross-sectional area and a second end 154 with asubstantially constant cross-sectional area larger than thecross-sectional area of the first end 152. A body 156 extends from thefirst end 152 to the second end 154. The body includes a firstlongitudinal length 158 proximate the first end 152 having across-sectional area substantially equal to the cross-sectional area ofthe first end 152, a second longitudinal length 160 proximate the secondend 154 having a cross-sectional area substantially equal to thecross-sectional area of the second end 154 and a sloped length 162diverging outwardly from a central axis "B" of the sleeve 150 as thesloped length 162 transitions from the first longitudinal length 158 tothe second longitudinal length 160. The body 156 has a substantiallysmooth outer surface 166 and a hollow inner bore defining asubstantially smooth inner surface 164. The substantially smooth outersurface 166 of the sleeve 150 precludes seams or interruption to beformed in the encapsulation 20 thus, eliminating areas which aresusceptible to, inter alia, predations of the environment. Theprotective sleeve 150 is fitted onto the coil and cable assembly 112 byplacing it over an end opposite the stripped end 122 and moving it intoengagement with the coil 90. The second end 154 of the sleeve 150 isplaced flush with the front face 94 of the coil 90. An inner surface 162of the protective sleeve 150 may be provided with an adhesive at one ormore points so that it may adhere to the preform 40. The preform has ataper 41 adjacent the coil to underlie the slope 162 in correspondingtight engagement. End 154 of sleeve 150 snugly overlies annular surface104 of coil 90. The constant cross-section near end 152 overlies agroove 39 in the preform 40 to assure the preform is located properly by"snapping" into place because of groove 39. Once the sleeved coil andcable assembly 170 (FIG. 8) is formed, it is reader to be encapsulated.

Referring to FIGS. 9 and 11, an injection mold 180 is defined by anupper mold plate 182 having an upper cavity 184 and a lower mold plate186 having a lower cavity 188 forming a single mold cavity 190 when inthe closed position. The mold cavity 190 is shaped complementary to thedesired form of the encapsulation 20 of the sleeved coil and cableassembly 170. The mold cavity 190 is defined by an upper wall 192, alower wall 194, a front wall 196 and a back wall 198 having an opening200 extending therethrough.

The upper mold plate 182 is provided with at least one sleeve 212athrough which at least one slideable support pin 210a may be moved intoor out of the upper cavity 184 by a drive means 230a. The lower moldplate 186 is preferably provided with a pair of sleeves 212b, 212cthrough which a pair of slideable support pins 210b, 210c may be movedinto or out of the lower cavity 188 by corresponding drive means 230band 230c. In addition, the injection mold 180 is provided with aslideable locator pin 220 which is preferably disposed on the lower moldplate 186 at a location adjacent the front wall 196 of the mold cavity190. The slideable locator pin 220 preferably includes a pair ofconcentrically disposed slideable pins 222, 224 in which an inner pin222 slides within an outer pin 224 which in turn slides within a sleeve226. Both the inner pin 222 and the outer pin 224 may be moved by anassociated drive means 230d such that they are capable of extending intoor out of the lower cavity 188 when the mold 180 is in the openedposition. Preferably, the inner pin 222 is capable of extending furtherinto the lower cavity 188 than the outer pin 224.

Alternatively, the slideable locator pin 220 may be fixed which would betantamount to an integrally formed T-shaped pin having a top branchresembling the outer pin 224 and a base branch resembling the inner pin222 in an extended and rigidly fixed position with respect to the topbranch.

The slideable support pins 210a-210c and the slideable locator pin 220are each preferably provided with separate drive means, 230a-230drespectively and may be independently controlled by a programmable logiccontroller (PLC) 250 or the like.

Each drive means 230a-230d includes a valve and solenoid unit 232a-232d,a pneumatic cylinder 234a-234d and an ejector plate 236a-236d. Eachejector plate 236a-236c is connected to each respective support pin210a-210c and ejector plate 236d is connected to locator pin 220. Eachejector plate 236a-236d is received within the corresponding pneumaticcylinder 234a-234d which in turn is connected to the corresponding valveand solenoid unit 232a-232d. Each valve and solenoid unit 232a-232d iselectrically connected to the PLC 250 and mechanically connected to agas source 260. The PLC 250 independently sends out an electrical signalto each solenoid of each valve and solenoid unit 232a-232d. Eachsolenoid receives the signal and physically opens and closes thecorresponding valve. This allows gas to be sent to each respectivepneumatic cylinder 234a-234d and depending on the location of eachejector plate 236a-236d will cause each support pin 210a-210c andlocator pin 220 to extend into or retract out of the mold cavity 190.The ejector plate 236d may be coupled to the inner pin 222 such that theinner pin 222 extends or retracts a short distance and then catches theouter pin 224 and causes it to correspondingly extend or retract.

When the injection mold 180 is in the closed position preferably onlythe support pins 210a-210c are used to support and symmetrically locatethe sleeved coil and cable assembly 170 within the mold cavity 190 (FIG.11). Depending upon the specific assembly 170 configuration and the waymolten moldable material is filling around the assembly 170, one of thesupport pins may be retracted sooner than another. Retracting thesupport pins is sequenced with the timing in the PLC 250 and may becalibrated until all of the support pins 210a-210c retract in a mannerwhich allows the assembly 170 to remain centered both radially andaxially within the mold cavity 190. Note that if the retraction of thesupport pins 210a-210c is not sequenced correctly the assembly 170 mayshift to one side or the other in the mold cavity 190. This may cause analteration of the electrical characteristics of the encapsulatedtransducer 10.

Referring to FIG. 10, the coil and cable assembly 170 is radially andaxially centered by way of the extended support pins 210b, 210c and anextended locator pin 220. The locator pin 220 centers the coil 90 andspaces it a predetermined distance from the front wall 196 of the moldcavity 190 by way of the inner pin 222 being partially received withinthe void 92 of the coil 90 and the outer pin 224 abutting against afront face 94 of the coil 90. In addition, support pin 210c is extendedinto the lower cavity 188 and placed in engagement with an end 152 ofsleeve 150, now part of the preform 40 for providing support thereto.Support pin 210b also extends into the lower cavity 188 and abuts acylindrical portion 40a of the protective preform 40 adjacent an endnear cable 120. In addition, a slot such as groove 150b may be providedon preform 40 to locate the engagement of the support pins 210b, 210cwith the preform 40 and the protective sleeve 150 respectively. Sleeve150 could have a locating aperture 150c to help locate pin 210c ingroove 39 (FIG. 8). Once the sleeved coil and cable assembly 170 hasbeen centered within the lower cavity 188, the locator pin 220 iswithdrawn and the mold cavity 190 is placed in a closed position (FIG.11). At this time, the front face 94 of the coil 90 is precisely spacedfrom the front wall 196 of the mold cavity 190. This allows theencapsulation 20 of the encapsulated traducers 10 to include theintegrally formed protective wall 26 having a substantially uniformthickness "T" (FIG. 2) and thus, a predetermined linear range. This isparticularly important when manufacturing a plurality of encapsulatedtransducers 10 which are to have uniform electrical characteristics.Furthermore, once the mold 180 is closed the cable 120 extends out ofthe opening 200 in the back wall 198 of the mold cavity 190. Theengagement of the upper mold plate 182 and the lower mold plate 186provides additional support by having the cable 120 cantileveredtherebetween. Support pin 210a extends into the upper cavity 184 fromthe upper mold plate 182 and comes into engagement with the preform 40of the cable 170 thereby providing a top support to the sleeved coil andcable assembly 170. A void completely surrounds the sleeved coil andcable assembly 170 except of course where the pins 210a-210c areabutting the assembly 170. An alternative embodiment to FIG. 11 may usefewer or more support pins 210a-210c for centering and supporting thesleeved coil and cable assembly 170 in the mold cavity 190.

The moldable material is injected into the mold cavity via runners 240(FIG. 11) and gates 242 provided in the lower mold plate 182 and/or theupper mold plate 186. It is preferred that a gate 242 be providedadjacent each support pin 210a-210c. Preferably, the moldable materialis polyphenylene sulfide (PPS) which has the characteristic of bondingto itself. The injection of the moldable material is continued until themold cavity 190 is completely filled. Once the mold cavity 190 isfilled, the support pins 210a-210c are sequentially or simultaneouslyretracted such that the sleeved coil and cable assembly 170 remainscentered within the mold cavity 190. Note that an additional charge ofmoldable material may be introduced into the mold cavity 190simultaneously with the retractions of the support pins 210a-210c suchthat the sleeved coil and cable assembly 170 is completely ensconcedwithin the moldable material and all voids have been filled.

Referring to FIG. 12, once the process of injecting the moldablematerial into the mold cavity 190 is completed and the support pins210a-210b have been retracted, the mold 180 may be opened and theencapsulated transducer 10 allowed to cool in the lower mold plate 186.Once the encapsulated transducer is cooled one or more of the bottomsupport pins, 210b, 210c may be actuated to eject the encapsulatedtransducer 10 therefrom.

In mass production it is preferred that an injection molding device beprovided which includes a single upper mold plate 132 and a plurality oflower mold plates 186 disposed on a rotatable table 270 (FIG. 13). Thelower mold plates 186 may each be preloaded with a single sleeved coiland cable assembly 170. Then, the upper mold plate 182 comes down ontothe first inline lower mold plate 186 and the respective sleeved coiland cable assembly 170 is encapsulated. Once the encapsulation processis completed the upper mold plate 182 is lifted and the table 270 isrotated about arrow "R" to align a subsequent lower mold plate 186 withthe stationary upper mold plate 182 so that the encapsulation processmay be repeated.

Meanwhile, the previously encapsulated transducer 10 may remain withinthe lower mold plate 186 and be allowed to cool as the table is rotatedand then ejected as delineated above. Now, after the encapsulatedtransducer 10 is ejected the lower mold plate 186 is reloaded with asleeved coil and cable assembly 170 and extends back to the upper moldplate 182 as the table 270 is rotated. This process may continue forencapsulating a batch of sleeved coil and cable assemblies 170.

In use and operation, and referring to FIGS. 1 and 2, the encapsulatedtransducer 10 may, for example, be utilized as a proximity transducerfor monitoring the vibrational characteristics of a rotating shaft 282of a machine 280. In this environment the encapsulated transducer 10operates on the eddy current principle and outputs a signal correlativeto the spacing between the rotating shaft 282 and the sensing coil 90 ofthe encapsulated transducer 10.

Typically, the encapsulated transducer 10 is circumscribed by a threadedmetal case 284 which is mounted adjacent the rotating shaft of themachine 280. A mounting means 286 is used to strategically mount theencapsulated transducer 10 such that the sensing coil 90, proximate thefront end 22 of the encapsulation 26, and the rotating shaft 282 are ina juxtaposed relation. The sensing coil 90 is electrically andmechanically connected to the cable 120. The cable 120 extends out theback end 24 of the encapsulation 20 and runs through a casing 288 of themachine 280 where it preferably terminates to a connection 290 capableof directly coupling to an electrical processing unit 310 or to anextension cable which in turn couples to the electrically processingunit 310.

Preferably, the cable 120 is routed through the machine case 288 bypassing through a rubber grommet 294 internal to an adaptor 292operatively coupled to the machine case 288. The adaptor 292 includes afirst end 296 having external and internal threads. The external threadsof the adaptor are coupled with a threaded bore 300 in the machine case288 for firmly connecting the adaptor 292 thereto. In some instances,the internal threads of the first end 296 of the adaptor 292 allow themounting of the encapsulated transducer 10 via the threaded metal case284. A second end 298 of the adaptor 292 having external threads may becoupled to a threaded aperture 304 in a junction box 302 such that thejunction box 302 is mounted to the machine case 288. The junction box302 allows any electrical connections operatively coupling the cable 120to the electrical processing unit 310 to be enclosed in a weather-proofor explosion-proof environment.

In addition to use as a proximity transducer, the present invention maybe employed very broadly in the monitoring and diagnostic field. Oneexample is as a temperature transducer which would use a coil formedfrom a single wire thermocouple of the RTD type. The coil would bemolded within the encapsulation 20 and the only change in the abovedelineated process may be in the use of perhaps a thinner overallencapsulation. This would provide for a suitable heat transfer to theRTD temperature sensing coil.

Moreover, having thus described the invention, it should be apparentthat numerous structural modifications and adaptations may be resortedto without departing from the scope and fair meaning of the instantinvention as set forth hereinabove and as described hereinbelow by theclaims.

I claim:
 1. An information transmitting sensor and housing comprising:asensing element; a cable coupled to said sensing element; a componentalignment preform operatively coupled to said sensing element and saidcable; a protective sleeve including a body having a substantiallysmooth outer surface and extending from said sensing element over saidpreform and towards said cable; and a monolith of cured moldablematerial ensconcing said sensing element and extending seamlessly alongsaid substantially smooth outer surface of said sleeve and ensconcing aportion of said cable defining a seamless mass circumscribing saidsensing element and a portion of said cable.
 2. The sensor of claim 1further comprising said component alignment preform disposed within saidmonolith of cured moldable material, said preform including a front endhaving an annular recess and a center post, a back end having an openingand a medial portion interposed between said front end and said rear endof said preform, said medial portion having a chamber in opencommunication with the opening in said back end.
 3. The sensor of claim2 wherein said component alignment preform includes a front ferrule anda rear ferrule bonded thereto and linearly spaced apart by said chamberalong a long axis of said sensor and in open communication with saidchamber.
 4. The sensor of claim 3 wherein a front passage and a rearpassage within said component alignment preform are in opencommunication with said front and rear ferrules respectively.
 5. Thesensor of claim 4 wherein said sensing element is a coil having a frontface, a back face and a body having an outer surface and a center voidextending therethrough, said body extending between said front face andsaid back face.
 6. The sensor of claim 5 wherein said coil is disposedwithin said annular recess of said preform and receives said center postwithin the center void of said coil thereby axially aligning said coilwith said front and rear ferrules along the long axis of said sensor. 7.The sensor of claim 6 wherein said first lead extends into the frontpassage of said preform and is electrically connected to said frontferrule.
 8. The sensor of claim 7 wherein said second lead extends intothe rear passage of said preform and is electrically connected to saidrear ferrule.
 9. The sensor of claim 8 wherein said cable includes atleast a center conductor and a coaxial conductor separated from oneanother by at least one dielectric.
 10. The sensor of claim 9 wherein atleast one end of said cable is stripped in a step-like fashion to exposea length of at least said center conductor, dielectric and coaxialconductor.
 11. The sensor of claim 10 wherein said stripped end of saidcable passes through the opening in said back end of said perform andsaid center conductor is electrically and mechanically connected withina bore of said front ferrule and said coaxial conductor is electricallyand mechanically connected within a bore of said rear ferrule.
 12. Thesensor of claim 11 including a seal circumscribing said dielectric atthe stripped end of said cable and wedged between said dielectric andsaid chamber of said preform thereby providing a barrier therebetween.13. The sensor of claim 12 wherein said protective sleeve includes afirst end with a substantially constant cross-sectional area and asecond end with a substantially constant cross-sectional area greaterthan the first end and said body having said substantially smooth outersurface and a hollow inner bore defining a substantially smooth innersurface, said body extending between said first end and said second end.14. The sensor of claim 13 wherein said body of said sleeve includes afirst longitudinal length proximate said first end having across-sectional area substantially equal to the cross-sectional area ofsaid first end and a second longitudinal length proximate said secondend having a cross-sectional area substantially equal to thecross-sectional area of said second end and a sloped length divergingoutwardly from a central axis of said sleeve as said sloped lengthtransitions from said first longitudinal length to said secondlongitudinal length.
 15. The sensor of claim 14 wherein said sleeve fitsover said coil and is attached to said preform such that said second endof said sleeve is substantially flush with said first face of said coiland said body of said sleeve extends beyond said back face of said coil.16. The sensor of claim 15 wherein said component alignment preform andsaid sleeve are formed from said moldable material.
 17. The sensor ofclaim 16 wherein said monolith of cured moldable material bonds withsaid preform and said sleeve.
 18. The sensor of claim 17 wherein saidmonolith of cured moldable material contacts and contours to the frontface of said coil and uniformly extends therefrom to form asubstantially uniform thick wall substantially parallel with said frontface of said coil.
 19. The sensor of claim 18 wherein said monolith ofcured moldable material ensconces a length of said cable proximate theback end of said preform where the cable emanates therefrom.
 20. Atransducer for monitoring the status of rotating equipment wherein ashaft of the rotating equipment is exposed to said transducer,comprising, in combination:means for mounting said transducer a distancefrom the shaft such that a tangent of the shaft is perpendicular to along axis of said transducer, said transducer having a sensing coillocated proximate the shaft, a front portion of said transducerincluding a protective wall having uniform thickness along a forwardmostportion of said sensing coil, said sensing coil symmetrically disposedabout the long axis, and a protective seamless encapsulation integrallyformed with said protective front wall ensconcing said sensing coil andoverlapping and extending seamlessly along a substantially smooth outersurface of a preform sleeve and overlapping a leading portion of a cableoperatively coupled to said sensing coil, said cable extending away fromsaid transducer to an electrical processing unit.
 21. An informationtransmitting sensor, comprising, in combination:means for mounting saidsensor a distance from a shaft such that a tangent of the shaft isperpendicular to a long axis of said sensor, said sensor having asensing coil located proximate the shaft, a front portion of said sensorincluding a protective wall having uniform thickness along a forwardmostportion of said sensing coil, said sensing coil symmetrically disposedabout the long axis, and a protective sleeve including a body having asubstantially smooth outer surface, said protective sleeve extendingaway from said protective wall and covering said sensing coil; aprotective seamless encapsulation integrally formed with said protectivefront wall ensconcing said sensing coil and overlapping and extendingseamlessly along said substantially smooth outer surface of saidprotective sleeve and overlapping a leading portion of a cableoperatively coupled to said sensing coil, said cable extending away fromsaid transducer to an electrical processing unit.